The field of this disclosure relates to vehicle engines, specifically to two-stroke cycle, opposed-piston engines constructed for compression ignition.
Ambient environmental conditions can affect combustion behavior of a compression-ignition engine. For example, a compression-ignition engine installed in a vehicle frequently requires assistance when starting cold in low temperature conditions. In this regard, effective combustion is dependent on achieving a high temperature by compression of air in the bore of a cylinder. However, under cold ambient and engine conditions the air drawn into the engine may be too cold to support combustion when the engine is started. Further, as the engine is cranked, the heat of compression is drawn away from the combustion chamber by the cold engine parts. In some cases, for example during winter, a minimally-equipped compression-ignition engine may require long periods of cranking in order to raise the temperature of the combustion chamber elements to a level that supports ignition, effective combustion, and minimal pollution.
A compression-ignition engine may be equipped with one or more of glow plugs, block heaters, intake heaters, ether injection, and/or other aids to facilitate start-up under cold conditions. However, these solutions bring added complexity and expense to the construction and operation of such an engine.
An opposed-piston engine is a type of compression-ignition engine in which effective combustion is dependent on achieving a high temperature by compression of air between adjacent end surfaces of a pair of pistons disposed for opposed movement in the bore of a cylinder. Advantages in engine architecture and two-stroke operation enable opposed-piston engines to deliver superior fuel, weight, and volume efficiencies when compared with conventional single-piston compression-ignition engines. A two-stroke cycle, opposed-piston engine must be able to start quickly and operate effectively in cold ambient conditions, with as little derogation of its inherent advantages as possible. It is therefore desirable to provide a strategy for starting a compression-ignition, opposed-piston engine under cold conditions while minimizing any added complexity and expense.